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A. M. López-Periago, C. A. García-González and C. Domingo,
Chem. Commun., 46, 4315 - 4317, (2010) DOI: 10.1039/c0cc00077a
The synthesis of Schiff base macrocycles was achieved using supercritical CO2 as both solvent and acid catalyst.
Over the past few years, the investigation of the synthesis of chiral imine macrocycles has become of growing interest.1 These Schiff based symmetric macrocyclic compounds offer an enormous potential in host–guest chemistry and molecular recognition, besides their additional potential applications as ligands and organocatalysts in asymmetric synthesis.2–3 The preparation of large polyimine meta- and para-macrocycles, also called trianglimines, has been successfully achieved using a classic synthetic strategy based on a [3+3] cyclocondensation (Scheme 1),4–7 where 3 units of (1R,2R)-diaminocyclohexane (1a) react with 3 units of an aromatic dialdehyde, either 1,3- (2) or 1,4-diformylbenzene (3), in a standard 0.4 M concentration in dichloromethane (DCM), yielding species 4a or 5a, respectively.